We don't have any synonyms for syne yet.
Think syne belongs in the thesaurus? Recommend it and we'll take a look.
Definition of syne:
(adv) :
(Scotland, Northern England) Before now; ago.
(adv) :
(Scotland, Northern England) Subsequently; then.
(adv) :
(Scotland, Northern England, chiefly in phrases like "soon as syne") Late.